# SPDX-License-Identifier: Apache-2.0
# SPDX-FileCopyrightText: Copyright contributors to the vLLM project
"""Tests that validation_exception_handler populates the `param` field
in its error response using the Pydantic error's `loc`, even when no
custom VLLMValidationError context is present.

Previously, `param` was only populated for errors carrying a custom
VLLMValidationError in their Pydantic `ctx`. Plain validation failures
(missing fields, wrong types) left `param` as None, even though the
field name was readily available from `error['loc']`.
"""

import json
from types import SimpleNamespace

import pytest
from fastapi.exceptions import RequestValidationError

from vllm.entrypoints.serve.utils.server_utils import validation_exception_handler


def _fake_request(log_error_stack: bool = False) -> SimpleNamespace:
    """Minimal stand-in for a FastAPI Request - just enough for the
    handler to read req.app.state.args.log_error_stack."""
    return SimpleNamespace(
        app=SimpleNamespace(
            state=SimpleNamespace(args=SimpleNamespace(log_error_stack=log_error_stack))
        ),
        state=SimpleNamespace(),  # no request_metadata -> hasattr(...) is False
    )


class TestValidationErrorParamFallback:
    """Ensure `param` falls back to the Pydantic error's `loc` when no
    custom VLLMValidationError context is present."""

    @pytest.mark.parametrize(
        ("error_type", "msg"),
        [
            ("missing", "Field required"),
            ("list_type", "Input should be a valid list"),
        ],
        ids=["missing-field", "wrong-type"],
    )
    @pytest.mark.asyncio
    async def test_param_falls_back_to_loc(self, error_type: str, msg: str):
        errors = [{"type": error_type, "loc": ("body", "messages"), "msg": msg}]
        exc = RequestValidationError(errors)

        response = await validation_exception_handler(_fake_request(), exc)
        body = json.loads(response.body)

        assert body["error"]["param"] == "body.messages"

    @pytest.mark.asyncio
    async def test_param_fallback_does_not_crash_on_non_dict_error(self):
        """Schemathesis fuzzing found that errors[0] isn't always a dict.
        The fallback must not crash in that case - it should just leave
        param as None instead of raising."""
        exc = RequestValidationError(["some unexpected non-dict error"])

        response = await validation_exception_handler(_fake_request(), exc)
        body = json.loads(response.body)

        assert body["error"]["param"] is None